Furnace having walls defined by tube membranes

ABSTRACT

The furnace of a waste liquor recovery furnace is often defined by water tube membranes. The chemical residue formed as a result of the combustion is likely to react forcibly when mixed with water, and every caution should be taken in the design to avoid the risk of tube leaks. The corner connection between two wall membranes is difficult to arrange, and if a strong combustion puff should occur the weld seams at the corner tube may cause a leak from which water could gush into the molten residues causing an explosion. To avoid this risk the corner tubes are free from the adjacent membranes, but are retained thereto by means of special clamping means.

United States Patent [191 Astrom Oct. 29, 1974 [5 FURNACE HAVING WALLSDEFINED BY 2,368,265 1/1945 Shellenberger 122/6 A TUBE MEMBRANES3,404,663 10/1968 Lewis et al 122/367 R Inventor: Ingmar Astrom,Stenungsund,

Sweden Gotaverkens Angtekniska AB (Gotaverken Heat Engineering Co.,Ltd.), Goteborg, Sweden Filed: June 1, 1973 Appl. No.: 366,115

Assignee:

Foreign Application Priority Data June 19, 1972 Sweden 8035/72 U.S. Cl.122/6 A, 122/235 A Int. Cl. F22b 37/00 Field of Search 122/6 A, 235 A,7; 110/98 References Cited UNITED STATES PATENTS 8/1934 Toomey 122/6 A12/1935 Selaya 122/6 A Primary Examiner-Kenneth W. Sprague AssistantExaminer-Larry l. Schwartz Attorney, Agent, or FirmPierce, Scheffler &Parker [5 7 ABSTRACT The furnace of a waste liquor recovery furnace isoften defined by water tube membranes. The chemical residue formed as aresult of the combustion is likely to react forcibly when mixed withwater, and every caution should be taken in the design to avoid the riskof tube leaks.

The corner connection between two wall membranes is difficult toarrange, and if a strong combustion puff should occur the weld seams atthe comer tube may cause a leak from which water could gush into themolten residues causing an explosion.

To avoid this risk the corner tubes are free from the adjacentmembranes, but are retained thereto by means of special clamping means.

1 Claim, 1 Drawing Figure FURNACE HAVING WALLS DEFINED BY TUBE MEMBRANESBACKGROUND OF THE INVENTION The furnaces of many combustion plantsnowadays often have walls consisting of tube membranes, i.e., spacedwater tubes interconnected by means of fins or similar members weldedtogether to form a flat unit. The tubes of these membranes are oftencovered by some protecting cladding, which may consist of a fireresistant compound stamped onto the wall, or of blocks of fire andcorrosion resistant material in any suitable manner attached to thewall.

With certain types of furnaces the risk of explosions or forceful puffsof combustion gases is imminent. So is for instance the case withdifferent types of refuse and waste combustion furnaces, especiallyfurnaces for the combustion of waste liquor from the cellulose pulpmanufacture. During the combustion of such liquor a chemical residue isformed at the bottom of the hearth, and if water from a cracked tubecomes into contact with this residue a forceful explosion will occur,which will deform the walls and may result in more tubes being cracked.

SUMMARY OF THE INVENTION Furnaces of this type are often designed with aquadrilateral cross section, and the damages are most likely to occurnear the corners of the furnace. The membranes are fitted at an angle tothe tube forming the corner, and if the walls, following an explosion,are bent outwards the attachments at the corner tube will be heavilystressed, which easily will lead to a cracking of some tube, or tubes.According to the invention the furnace is therefore designed in such amanner, that a tube located at each corner of the furnace is free fromthe adjacent membranes and is connected to the latter by means of clampsarranged externally of the walls and adapted for securing the blocks tothe walls, said clamp at the pertaining corner tube extending to eachdirection therefrom at least over the outermost tube in the adjacentmembrane.

BRIEF DESCRIPTION OF THE DRAWING The drawing shows by way of example acorner portion of a furnace belonging to a waste liquor combustionplant.

DESCRIPTION OF THE PREFERRED EMBODIMENT The walls of the furnace arecomposed of a number of water tubes 10, which within each side wall ofthe furnace are welded together to membranes. The faces of the tubesturned towards the furnace are covered by blocks 11 of fire resistantmaterial, which are forced towards the tubes by means of wedge shapedmembers 12. These are retained at the wall by means of clamps I3 andbolts 14.

According to the invention two membranes arranged at an angle to eachother and meeting each other at a corner are not interconnected directlyby welding, but are locked together by means of a separate tube 15,which forms part of the water circulation system, but is not welded toeither of the membranes. Tube 15 is, however, connected to the adjacentmembranes by means of the clamps 13 used for retaining the wedge shapedmembers 12 at the corner portion. These clamps are designed in such amanner that they from the corner tube extend over at least one,preferably over two tubes in the adjacent membrane.

It is evident that the walls of big furnaces may each contain more thanone membrane, so a single unit does not extend from one corner tube tothe other. It is further evident that the shape of the blocks and of thewedge members, as well as of the clamps is not limited to the examplesshown in the drawing, but will have to be suited to the actualapplication. The essential part is that the corner tubes are free fromthe membranes, and that the clamps at the corners have sufficient lengthto provide the required strength.

What I claim is:

I. In a steam boiler furnace having parallel water tubes interconnectedby welding to form tube membranes, said membranes being assembled todefine a combustion chamber having quadrilateral cross section and beingprovided, at their faces turned towards the combustion chamber, withblocks of fire-resistant material secured by clamping means locatedoutside the wall,

the improvement of a water tube located at each corner of the combustionchamber, said tube lacking permanent connection of the adjacent tubemembranes;

block retaining clamping means extending over the pertaining corner tubeand at least the outermost tube in each of the adjacent tube membranesthereby locking said corner tube to said adjacent membranes; and

web-shaped blocks of fire-resistant material secured by saidblock-retaining clamping means to the faces of said corner tubes turnedtoward said chamber.

1. In a steam boiler furnace having parallel water tubes interconnectedby welding to form tube membranes, said membranes being assembled todefine a combustion chamber having quadrilateral cross section and beingprovided, at their faces turned towards the combustion chamber, withblocks of fireresistant material secured by clamping means locatedoutside the wall, the improvement of a water tube located at each cornerof the combustion chamber, said tube lacking permanent connection of theadjacent tube membranes; block retaining clamping means extending overthe pertaining corner tube and at least the outermost tube in each ofthe adjacent tube membranes thereby locking said corner tube to saidadjacent membranes; and web-shaped blocks of fire-resistant materialsecured by said block-retaining clamping means to the faces of saidcorner tubes turned toward said chamber.